1. Field of the Invention
This invention relates generally to a method for synthesizing metal and metal oxide nanoparticle-embedded composites and compositions of same.
2. Background of the Invention
Nanocomposites of inorganic materials in polymer matrices have attracted a great deal of attention because of their wide applications as biosensors, optical devices, micromechanical devices and advanced catalytic membranes. [M. T. Sulak, et al. Biosensors & Bioelectronics 2006, 21, 1719; S. Dire et al., Journal of Materials Chemistry 1992, 2, 239; H. Chen et al., Advanced Materials 2006, 18, 2876; H. Chen et al., Advanced Materials 2006, 18, 2876]. For the synthesis of nanocomposites, different approaches have been developed, such as the incorporation of pre-made nanoparticles into a polymer matrix with the use of a common blending solvent or by reduction of metal salt dispersed in polymeric matrix using an external reducing agent. [J. H. Park et al., Chemistry of Materials 2004, 16, 688]. Nanoparticles can also be embedded in polymers using physical and chemical vapor deposition, ion-implantation and sol-gel synthesis routes. [K. S. Giesfeldt et al., Applied Spectroscopy 2003, 57, 1346; E. W. Kreutz et al., Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms 1995, 105, 245; I. Yoshinaga et al., Journal of Sol-Gel Science and Technology 2005, 35, 21]. Using these approaches, various metal nanoparticle-polymer composites have been synthesized including gold-poly(9,9-dioctylfluorene) for light emitting diodes and iron-poly(methylmethacrylate) for electromagnetic applications. [J. L. Wilson et al., J. Appl. Phys. 2004, 95, 1439]. Gao et al. have used palladium-containing hollow polymeric fibers of cellulose acetate, polysulfone, and polyacrylonitrile as catalytic membrane reactors for selective hydrogenation of conjugated dienes. [H. R. Gao et al., J. Membr. Sci. 1995, 106, 213].
Polydimethylsiloxane (PDMS) elastomer is one such polymer that has been utilized when synthesizing nanocomposites. PDMS has many useful properties, such as high flexibility, ease of molding, low cost, non-toxic nature and chemical inertness. [J. N. Lee et al., Anal. Chem. 2003, 75, 6544 (“Lee et al.”)]. PDMS has been used extensively in applications that include microfluidic channels, lubricants, defoaming agents, gas separation membranes and catheters. [F. Abbasi et al., Polymer International 2001, 50, 1279]. In spite of its wide use, it has some inherent drawbacks, such as mechanical weakness and intolerance to organic solvents. [Lee et al.]. Metal nanoparticle containing film can show enhanced mechanical properties as well as imparts multifunctionality like catalysis and gas separation capability. Therefore, attempts have been made to synthesize metal nanoparticles embedded PDMS films. Gao and co-workers have reported chitosan assisted gold nanoparticle deposition on PDMS surfaces. [B. Wang et al., Biomacromolecules 2006, 7, 1203]. Chen and co-workers synthesized gold nanoparticle-PDMS composite films by immersing cured PDMS films in gold chloride solution. These films were used for enzyme immobilization and as a chemical reactor. However, their synthesis method involves multiple steps and the nanoparticle concentration is localized to the surface only. [Q. Zhang et al., Lab on a Chip 2008, 8, 352 (“Zhang”)].
Consequently, there is a need for an improved process for synthesizing metal and metal oxide nanoparticle-embedded composites. The term “metal” refers collectively to a pure metal (i.e., one type of metal, such as silver, gold, etc.) and a metal alloy (i.e., mixtures of two or more metals, such as PdFe, PdNi, etc., or mixtures of one or more metals with certain nonmetallic elements, such as carbon steel). Coordinately, the term “metal oxide” refers collectively to an oxide of a pure metal (i.e., an oxide of one type of metal, such as iron oxide) and an oxide of an alloy of metals (i.e., an oxide of two or more metals, such as iron-copper oxide).